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I've seen some posters stating that strdup is evil. Is there a consensus on this? I've used it without any guilty feelings and can see no reason why it is worse than using malloc/memcpy.
The only thing I can think might earn strdup a reputation is that callers might misuse it (eg. not realise they have to free the memory returned; try to strcat to the end of a strdup'ed string). But then malloc'ed strings are not free from the possibility of misuse either.
Thanks for the replies and apologies to those who consider the question unhelpful (votes to close). In summary of the replies, it seems that there is no general feeling that strdup is evil per se, but a general consensus that it can, like many other parts of C, be used improperly or unsafely.
There is no 'correct' answer really, but for the sake of accepting one, I accepted @nneoneo's answer - it could equally have been @R..'s answer.
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Most C programmers are familiar with the strdup function. Many of them will take it for granted, yet it is not part of the C Standard (neither C89, C99 nor C11). It is part of POSIX and may not be available on all environments. Indeed Microsoft insisted on renaming it _strdup , adding to confusion.
Difference between strdup() and strcpy()The function strcpy() will not allocate the memory space to copy. A pointer to the string to copy and a pointer to place to copy it to should be given. The function strdup() will occupy / grab itself the memory space for copying the string to.
The strdup() function returns a pointer to a new string which is a duplicate of the string s. Memory for the new string is obtained with malloc(3), and can be freed with free(3). The strndup() function is similar, but copies at most n bytes.
In the case of strdup, we use a specific function, malloc(), to allocate the memory dynamically. But it is favorable if you delete the content or free the space after usage. So for this purpose, simply use strdup() with malloc(), and then copy the source string to the allocated memory.
Two reasons I can think of:
_strdup), and technically the C standard could define its own strdup with different semantics since str is a reserved prefix. So, there are some potential portability concerns with its use.str functions don't allocate memory, so users might be misled (as you say) into believing the returned string doesn't need to be freed.But, aside from these points, I think that careful use of strdup is justified, as it can reduce code duplication and provides a nice implementation for common idioms (such as strdup("constant string") to get a mutable, returnable copy of a literal string).
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My answer is rather supporting strdup and it is no worse than any other function in C.
POSIX is a standard and strdup is not too difficult to implement if portability becomes an issue.
Whether to free the memory allocated by strdup shouldn't be an issue if anyone taken a little time to read the man page and understand how strdup works. If one doesn't understand how a function works, it's very likely the person is going to mess up something, this is applicable to any function, not just strdup.
In C, memory & most other things are managed by the programmer, so strdup is no worse than forgetting to free malloc'ed memory, failing to null terminate a string, using incorrect format string in scanf (and invoking undefined behaviour), accessing dangling pointer etc.
(I really wanted to post this as a comment, but couldn't add in a single comment. Hence, posted it as an answer).
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